1. Field of Invention
The present invention relates to a liquid crystal display panel (LCD panel). More particularly, the present invention relates to an LCD panel capable of preventing mura.
2. Description of Related Art
From the first appearance of monochromatic TV sets working with cathode ray tubes (CRT), a tremendous progress has been made to the display technology. However, as displays working with the CRT have disadvantages of being large, heavy, high radiation, and low display quality, new flat display techniques have been developed successively. Among these flat display techniques, the liquid crystal display (LCD) technique is mature and popularized because of the advantages of being light, thin, short, and small, power saving, radiation free, full color, and convenient to carry. The LCD technique has been widely used in mobile phones, translation machines, digital cameras, digital video cameras, PDAs, laptop computers, and even desktop displays.
Generally speaking, an LCD displays images by adjusting the transmittance of liquid crystal cells of the LCD panel according to image signals. The LCD panel mainly includes a TFT array substrate, a color filter substrate, a liquid crystal layer, and a sealant. At least a plurality of pixels, various signal lines, and a common circuit layer are disposed on the TFT array substrate. The sealant is disposed between two substrates, so as to surround the liquid crystal layer and cover a part of the signal lines and the common circuit layer.
In order to reduce the impedance of the signal lines or the common circuit layer, the signal lines or the common circuit layer may include two metal film layers electrically connected with each other, or sometimes only one film layer. If the signal lines include a metal film layer and the common circuit layer includes two metal film layers, the thickness of the signal lines is different from that of the common circuit layer. As the signal lines and the common circuit layer have different thickness, the thickness of the sealant is different in different regions, which causes different cell gaps. Under this circumstance, curtain mura occurs around a display area of the LCD panel. On the contrary, if the signal lines include two metal film layers and the common circuit layer includes one metal film layer, the similar problem also occurs.
As described above, the signal lines or the common circuit layer can include two metal film layers electrically connected with each other, and the conductive materials of the two metal film layers are electrically connected together via structures such as contacts. However, electrostatic discharge (ESD) usually occurs at positions of the contacts. Therefore, designers of LCD panels should improve the structure of the signal lines.